1. Field of the Invention
The present invention relates to an electric double layer capacitor package and a method of manufacturing the same, and more particularly, to an electric double layer capacitor package allowing for an increase in a surge voltage and an operating voltage and a method of manufacturing the same.
2. Description of the Related Art
An electric double layer capacitor (EDLC) is an energy storage medium in which two electrodes of an anode and a cathode are arranged to face each other with a separator interposed therebetween so that a pair of charge layers (electric double layers) having different signs can be generated on the facing surfaces of the electrodes.
An EDLC is mainly used as an auxiliary power supply, an IC backup power supply or the like for a variety of electrical and electronic devices. In recent years, the EDLC has been widely used for applications including a toy, an industrial power supply, an uninterrupted power supply (UPS), solar energy storage, HEV/EV sub power, and the like.
An EDLC is generally manufactured by accommodating a unit cell in a case and then filling the case with an electrolyte. Here, the unit cell is constructed by stacking a pair of electrodes and a separator.
A pair of electrodes have a positive polarity (+) or a negative polarity (−) determined according to the sign of external electricity applied thereto. Terminals to which external electricity are applied are drawn from the pair of electrodes.
In the pair of electrodes, positive (+) charges and negative (−) charges are polarized, and accordingly, two charge layers (electric double layers) are formed in a single unit cell.
In a conventional unit cell, however, a surge voltage is low, i.e., less than 3.0V, and an operating voltage is also low, i.e., 2.3V to 2.7V. Therefore, there is a problem in that two or more EDLCs have to be connected in series in order to establish an operating voltage applicable to electronic products.
However, in a case where two or more EDLCs are serially connected to increase the operating voltage, there is another problem in that a balance problem between the EDLCs, which inevitably occurs, should be solved. Specifically, there is a need for a voltage balance protection circuit such as a resistor, a diode and another IC so that the overall operating voltage of the capacitors is not concentrated on a single EDLC, in consideration of the capacitance of each EDLC, equivalent serial resistance (ESR), a leakage current, and the like.
However, since voltage balance among the EDLCs is broken due to repeated cycles, there is a problem that a high voltage is applied to anyone of the EDLCs. This causes an electrolyte to be dissolved (the electrolyte is dissolved when a voltage of 3.0V or more is applied thereto). It also results in increased internal resistance, reduced capacitance, and the like.